Do gerbils have pouches? I'm not familiar with keeping them. If they don't, I dont' see a problem with gerbils.
If you take a stalk that hasn't been crushed anywhere and look at the end of it, it's hollow, like a straw or needle. So, if the end is not cut smoothly but on any kind of angle or unevenly, this is now sharp enough to puncture the toughest hides.
The softer leafy stuff is fine though. If they like it.
I made the mistake of buying a bag of the stuff in a pet store for my hamsters as well, and I was looking at the stuff and said, "this can't be too good for them with all the stems here." I just put the softer stuff in and no one touched it too.
I paid somthing like $3 for this tiny bag! I figured that if they go nuts for it I could get bales of it for the same price at my hay guy, where I bought hay for my horses.
This was when I first got my hamsters and at that time, I just found PWS. I never saw a dwarf before and frankly, didn't even know dwarf hamsters existed.
I kept Syrians as a kid, but that was a LOOOONG time ago and the information was little or non existant in regards to them. There wasn't a vet that would even look at or treat one. Sadly they were considered 'throw away pets'.
So as I got myself an education on hamsters I found I should not believe most anything the pet stores tell me, and use more common sense and caution before I buy what they stock. I read all ingredients and watch how many times sugar is on a list. [Those Vitakraft yogurt drops are nothing but sugar]. The feeding of excess sugar is bad for dwarfs and although it was thought that Robos don't get diabetes, [if I remember right] there is a couple of cases of diabetes found in Robos in the UK.
I also go by the rule of 'If you cannot pronounce it, it's NOT food'.
Now, I wind up going to several stores for my guys' food. I like the smaller Mazuri brand lab pellets for the dwarves that only PetSmart carries, and I found at PetCo, they have a 'food bar' of sorts where you can buy bird and small animal food by the pound. My guys love the hamster mix there and it works out better economically too. They just used to pick apart the pre packaged stuff and leave any of those bits that resemble kibble, leaving me to throw out more than they were eating.